Tim Furniss/LONDON

The launch of the NASA High Energy Transient Explorer (HETE) aboard a Pegasus booster from Vandenberg AFB, California, was cancelled in late January as the space agency considered it too risky. NASA wants more testing of the satellite and further preparations at ground stations before it goes ahead.

It has been revealed that the satellite's thermal vacuum testing was minimal, some components were replaced and no follow-up vibration testing was conducted.

The decision to cancel the launch comes after the failure of similar-class satellites and the loss of the Mars Polar Lander (MPL) and Mars Climate Orbiter last year.

Meanwhile, a radio antenna at Stanford University may have picked up a faint communication from the MPL. A signal has been sent by NASA's Jet Propulsion Laboratory to order the lander to communicate.

NASA says, however, that it is a "long shot" that the signal originated from the MPL.

Other NASA missions have encountered recent problems. The Earth Observing System flagship, the Terra, had the first in a series of orbital-raising burns aborted on 11 January after the flight computer detected a small roll on the craft. Engineers are working on ways to amend the software so the burns can continue. Glitches in the Terra's computer and high-gain antenna were corrected shortly after launch on 18 December.

Meanwhile, the last of three critical rocket burns by NASA Deep Space craft Stardust, lasting 33min, has been completed, placing it on its final course to the comet Wild 2 in January 2004. The Stardust will collect cometary material, returning it to Earth in 2006.

NASA has also had success with its Deep Space 1 New Millennium programme, with the spacecraft pointing its high gain antenna towards Earth. It had been in self-imposed safe mode since November, when a star tracker failed.

In addition, some of the observations made by NASA's Far Ultraviolet Spectroscopic Explorer indicate that an extended halo of 500,000°C gas surrounding the Milky Way was generated by thousands of exploding stars as the galaxy was formed.

Source: Flight International